Quick Java question

reptonite

Lads

This is the code for a VERY simple currency converter in Swing. I am after a fast and dirty way to limit the dollarAmount field to 2 decimal places. Is there any way of specifying it in the constructor?

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.JPanel;

public class Converter extends JPanel{
	JButton convert;
	JTextField euro;
	JTextField dollar;
	JTextField rate;
	JLabel euroLabel;
	JLabel dollarLabel;
	JLabel rateLabel;
	
	public Converter (){
		super();
		euroLabel = new JLabel ("Euro (€): ");
		dollarLabel = new JLabel ("Dollar ($): ");
		rateLabel = new JLabel ("Rate: ");
		
		euro = new JTextField ("0.00", 8);
		dollar = new JTextField ("0.00", 8);
		dollar.setEditable (false);
		rate = new JTextField ("1.27", 4);
		
		convert = new JButton ("CONVERT!");
		
		convert.addActionListener (new ActionListener (){
			public void actionPerformed (ActionEvent ae) {
				double euroAmount = Double.parseDouble(euro.getText());
				double r = Double.parseDouble(rate.getText());
				double dollarAmount = euroAmount*r;
				dollar.setText(""+ dollarAmount);
			}
		});
		add(euroLabel);
		add(euro);
		add(rateLabel);
		add(rate);
		add(convert);
		add(dollarLabel);
		add(dollar);
	}
	public static void main (String args[]){
		JFrame frame = new JFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.add(new Converter());
		frame.pack();
		frame.setVisible(true);
	}
}

Many thanks in advance...

smythmark

Something like this should do it

DecimalFormat df = new DecimalFormat("#,###.00");
double d = 1234.567;
System.out.println(df.format(d));

so for example 1234.678 becomes 1,234.57.

Barry.Commins

You could use a formatted text field and a decimal formatter.

You should also use dollar.setValue() instead of dollar.setText() in your ActionListener() if you want to limit the number of digits.

                //......
                
                DecimalFormat df = new DecimalFormat("#,###.##");
                df.setMinimumFractionDigits(2);
                df.setMaximumFractionDigits(2);
                
		dollar = new JFormattedTextField (df);

you will also need to set the number of columns and the the inital value for your formatted text field, but it's pretty straight-forward.

There are probably easier ways to do it, but this way should work fine.